In known circuit breakers of this type, a vertical control shaft connected to the control jack is used to actuate two levers which serve to drive respective rods which are connected to the contacts in the breaker chambers. Since the chambers and the support contain a gas under pressure (e.g. SF.sub.6), there are two varieties of circuit breaker:
In the first variety, the intermediate structure between the support and the breaker chambers is gas-tight and is filled with gas under pressure, in which case the gas circulates freely between the breaker chambers and the support. Under such circumstances it is not possible to dismantle any one component, e.g. one of the chambers, without completely emtying the entire circuit breaker of its gas, which then leads to problems during re-assembly since the entire circuit breaker must be dried and evacuated of air before SF.sub.6 is re-inserted therein. Thorough drying is most important.
In the second variety, the intermediate structure is not under pressure, which means that gas-tight sliding joints are required around the control shaft where it passes from the vertical support to the intermediate structure, and around the two rods where they pass from the intermediate structure into the respective breaker chambers.
Such sliding seals are difficult to make, and they are not always reliable.
The present invention provides a circuit breaker which includes an intermediate structure that is not filled with gas under pressure, and which is thus accessible thereby making it possible to disconnect gas communication between the various parts of the circuit breaker, thus enabling a single part (e.g. a breaker chamber) to be removed on its own.